// -*- c++ -*-
//------------------------------------------------------------------------------
//                              Fork.cpp
//------------------------------------------------------------------------------
//  Copyright (C) 1997-2003,2005  Vladislav Grinchenko
//
//  This library is free software; you can redistribute it and/or
//  modify it under the terms of the GNU Library General Public
//  License as published by the Free Software Foundation; either
//  version 2 of the License, or (at your option) any later version.
//------------------------------------------------------------------------

#include <iostream>
#include <fcntl.h>

#if !defined(WIN32)
#    include <syslog.h>
#endif

#include "assa/Fork.h"
#include "assa/CmdLineOpts.h"
#include "assa/SigAction.h"
#include "assa/EventHandler.h"
#include "assa/SigHandler.h"

using namespace ASSA;

//------------------------------------------------------------------------------
/*
 * Note the use of _exit () instead of exit () in the child's portion.
 * For some GUI toolkits, calling exit() causes problems.
 *
 * From Gtk+ (www.gtk.org) FAQ:
 *
 *  "When GDK opens an X display, it creates a socket file descriptor.
 *   When you use the exit() function, you implicitly close all the
 *   open file descriptors, and the underlying X library really
 *   doesn't like this. The right function to use here is _exit()."
 *
 * From UNIX exit(2) man page:
 *
 *  "The function _exit terminates the calling process "immediately".
 *   Any open file descriptors belonging to the process are closed;
 *   any children of the process are inherited by process 1, init, and
 *   the process's parent is sent a SIGCHLD signal."
 *
 * _exit() doesn't not call standard I/O cleanup routines.
 *
 * From S.A. Rago "Unix System V Network Programming", sec. 2.4, p.74
 *
 *  "When a child terminates, the operationg system sends the SIGCHLD
 *   signal to the parent process. The default disposition for SIGCHLD
 *   is to ignore the signal, but a process can catch the signal and
 *   obtain the status of its children."
 *
 * We also preserve the SIGCHLD action mask here and catch it to get
 * the child's completion status. SIGCHLD signal mask is initially set to
 * SIG_IGN by GenServer, but can be reset later on by a third-party library
 * linked into the application code.
 */
int
Fork::
fork_exec (const string& cmd_,
		   const string& args_,
		   Fork::wait4status_t wait_for_completion_,
		   bool ignore_output_)
{
    trace_with_mask("Fork[static]::fork_exec",FORK);

	DL((FORK,"exec \"%s %s\")\n", cmd_.c_str (), args_.c_str ()));
    if (cmd_.size () == 0) {
		return -1;
    }

#if defined(WIN32)

    return -1;    // NOT IMPLEMENTED YET

#else

    Fork f (Fork::LEAVE_ALONE, wait_for_completion_);

    if (f.isChild ()) {
		string arg_list (cmd_);
		arg_list += " " + args_;
		int argc = 0;
		char** argv = 0;
		CmdLineOpts::str_to_argv (arg_list, argc, argv);

		/** Close all file descriptors and reduped stdout/stderr
			to /dev/null
		*/
		if (ignore_output_) {
			for (int i = 0; i < 1024; i++) {
				(void) close(i);
			}
			pid_t nullfd = open("/dev/null", O_WRONLY | O_CREAT, 0666);
			if (nullfd == -1) {
				syslog (LOG_ERR,"failed to open \"/dev/null\"");
				_exit (-1);
			}

			(void) dup2  (nullfd, 1);
			(void) dup2  (nullfd, 2);
			(void) close (nullfd);
		}

		execvp (cmd_.c_str (), argv);

		EL((ASSAERR,"fork_exec (\"%s\") failed\n", cmd_.c_str ()));
		_exit (-1);
    }

    if (! wait_for_completion_) {
		return f.getChildPID ();
    }

	return f.get_exit_status ();

#endif // defined(WIN32)
}


#if !defined(WIN32)
//------------------------------------------------------------------------------
// Static declarations
//
ASSA_DECL_SINGLETON(ForkList);

//------------------------------------------------------------------------------
// Member functions
//
int
ChildStatusHandler::
handle_signal (int signum_)
{
	trace_with_mask("ChildStatusHandler::handle_signal", FORK);
	DL((FORK, "Caught signal # %d\n", signum_));

	if (signum_ == SIGCHLD) {
		int status;
		m_caught = true;
		pid_t ret = ::wait (&status);
		DL((FORK,"wait() = %d (PID)\n", ret));

		if (ret > 0 && (WIFEXITED (status))) {
			m_exit_status = WEXITSTATUS (status);
		}
		else {
			m_exit_status = ret;
		}
	}

	DL((FORK,"child exit_status = %d\n", m_exit_status));
	return 0;
}

//------------------------------------------------------------------------------
Fork::
Fork (Fork::state_t exit_action_, Fork::wait4status_t catch_status_)
{
	trace_with_mask("Fork::Fork",FORK);

	if (catch_status_ == COLLECT_STATUS) {
		m_local_sh.install (SIGCHLD, &m_chstath, 0, 0, &m_old_disp);
	}

	if ((m_pid = fork()) < 0) {
		EL((ASSAERR,"failed to fork() - out of swap space?\n"));
		exit (1);	                     // die right here
	}

	if (m_pid) {				         // The Parent
		if (exit_action_ != LEAVE_ALONE) {
			ForkList::get_instance()->m_list.push_back (new fnode_t (m_pid, exit_action_));
		}
		if (catch_status_ == COLLECT_STATUS) {
			if (! m_chstath.caught ()) {
				pause ();
			}
			m_local_sh.remove (SIGCHLD, &m_chstath, &m_old_disp, 0);
		}
	}
}


ForkList::
~ForkList()
{
    trace_with_mask("ForkList::~ForkList",FORK);

    list<fnode_t* >::iterator i;
    pid_t pid;

    // Go through the list and send SIGTERM to those children
    // whose flags were set at fork time.

    for (i = m_list.begin(); i != m_list.end(); i++) {
		if ((*i)->needKill()) {
			::kill((*i)->getPID(), SIGTERM);
		}
    }
    // Wait for all children to exit.

    while ( ! m_list.empty() ) { // wait for child to exit
		pid = ::wait(NULL);
		if ( pid < 0 ) { // error on wait
			EL((ASSAERR,"Error on wait()\n"));
			exit (EXIT_FAILURE);
		}
		// Search for child through the list by its pid.
		// If found, remove it from list and release memory.

		list<fnode_t* >::iterator j;

		for (j = m_list.begin(); j != m_list.end(); j++) {
			if ((*j)->getPID() == pid) {
				fnode_t* ep = *j;
				m_list.erase(j);
				delete ep;
				break;
			}
		}
    }
}

#endif // !defined(WIN32)